JP3209608B2 - Two-step injection molding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet print head, and more particularly to an ink jet print head having an ink manifold and a channel plate, and a method of manufacturing a manifold and a channel plate for the ink jet print head.

[0002]

2. Description of the Related Art In general, drop-on-demand type ink jet printing apparatuses can be divided into two types. Either a piezotransducer is used to generate a pressure pulse that ejects a droplet from the nozzle, or a type that uses thermal energy to create a vapor bubble in an ink-filled channel that ejects the droplet. The latter type is called thermal inkjet printing or bubble inkjet printing type. In current thermal ink jet printing, for example, as disclosed in U.S. Pat. No. 4,463,359 to Ayata et al. (The disclosure of which is incorporated herein by reference). Has one or more ink-filled channels, communicates at one end with a relatively small ink supply chamber, and at the opposite end has an opening called a nozzle. A thermal energy generator, typically a resistor (resistor), is located in the channel near the nozzle, separated by a predetermined distance. The resistors are individually addressed by current pulses to instantaneously vaporize the ink and form bubbles that eject ink droplets. As the bubbles become larger, the ink swells from the nozzles and is absorbed in a meniscus shape by the surface tension of the ink. As the bubble begins to collapse, the ink remaining in the channel between the nozzle and the bubble begins to move toward the collapsing bubble, resulting in a volumetric contraction of the ink at the nozzle. The swollen ink as droplets is separated. While the bubbles are growing, the acceleration of the ink ejected from the nozzles provides the momentum and velocity of the droplet that travels in a substantially linear direction toward the recording medium, such as paper.

[0003] US Patent No. 4,463,359 discloses a thermal ink jet printer having one or more ink filled channels that are replenished by capillary action. The meniscus is formed at each nozzle so that ink does not overflow from each nozzle. A resistor or heater is located within each channel at a predetermined distance from the nozzle. A current pulse representing the data signal is applied to the resistor, which instantaneously vaporizes the ink in contact with the resistor and forms a bubble for each current pulse. Ink droplets are ejected from each nozzle as the bubble grows, thereby causing a large amount of ink to bulge out of the nozzle and moving a large amount of ink toward the droplet at the onset of bubble collapse. Let it. The current pulse is
After each droplet is ejected, the meniscus is destroyed,
And it is formed so as to prevent the meniscus from retreating too much in the channel. One with a staggered linear array attached to the top and bottom surfaces of the heat sink substrate,
Various embodiments of a linear array thermal inkjet device, such as those having different color inks for multicolor printing, are shown. In one embodiment, a resistor is located in the center of a relatively short channel having nozzles at both ends of the channel. The other passage is connected to the open end channel and is perpendicular to the open end channel so as to form a T-shaped structure. By capillary action,
Ink is replenished from the passage into the open end channel. This allows two different recording media to be printed simultaneously when bubbles are formed in the open end channel.

One preferred technique for manufacturing thermal ink jet printheads is Hawkins.
s), issued to US Reissue Patent No. 32,572, the disclosure of which is incorporated herein by reference. Each printhead is composed of two parts that are aligned and glued together. The first part (known as the heater plate)
A substantially planar substrate including a linear array of heating elements and addressing electrodes on the surface. The second component (known as the channel plate) is a substrate having at least one recess that is anisotropically etched in the substrate so as to act as an ink supply reservoir when the two components are glued together. is there. The second part is formed with a linear array of parallel grooves whereby one end of the groove communicates with the reservoir recess and the other end of the groove is open for use as an ink drop ejection nozzle. Multiple sets of heating element arrays (heater plates) with addressing electrodes
Is manufactured on a silicon wafer, and a plurality of print heads can be manufactured simultaneously by arranging the alignment marks at predetermined positions on the silicon wafer. Corresponding sets of channels and corresponding reservoirs (channel plates) are fabricated in a second silicon wafer, and in one embodiment, alignment openings are etched into place thereon. The two wafers are aligned via the alignment openings and alignment marks, then glued together and diced into multiple separate printhead modules. A number of print head modules can be fixedly provided in a page width shape facing the moving recording medium for page width printing. Alternatively, individual printhead modules can be used to form a carriage-type printhead as shown in FIG. 1 of U.S. Pat. No. Re. 32,572.

[0005] Typically, these printheads are mounted on a heat sink, which causes the heater plate to be in physical contact with the heat sink. Each addressing electrode is wire bonded to a corresponding electrode on a printed wiring board (US Pat. No. Re. 32,57).
No. 2 (see FIGS. 2 to 4). Usually, the ink manifold is sealed to the surface of the channel plate opposite the surface having the channels, so that the ink in the ink supply chamber can be replenished to the reservoir in the channel plate via the ink manifold.

[0006] These ink manifolds can be made by a one-step injection molding process using hard plastic materials.

FIG. 1 is a block diagram of a conventional process for manufacturing a thermal ink jet printhead, such as the printhead shown in FIG. The hard plastic manifold 18 is injection molded (S1), and the heater plate 12 and the channel plate 15 are respectively manufactured in a silicon wafer (S2, S3). The heater wafer and the channel wafer are aligned by infrared rays, and the channel plate 15 of the channel wafer is bonded to the heater plate 12 of the heater wafer using the epoxy 13 to form a wafer assembly (S4, S5, S6). The wafer component is diced into a number of individual printhead modules 17 using a dicing blade, and the wafer component is cleaned by ultrasound. As a result, the individual print head modules 17 are separated from the diced wafer components (S7 to S9). To learn more about this manufacturing process, see, for example, US Pat. No. 4,782, issued to Campanelli et al.
6, 357 and the like.

After covering the nozzle-equipped front surface of each print head module with a hydrophobic substance, the adhesive for bonding each channel plate to the corresponding heater plate is entirely cured (S10). The printhead module 17 is then used to make either a carriage-type thermal inkjet printhead or a full-width thermal inkjet printhead. While full-width thermal inkjet printheads can be formed as butt or staggered arrays of individual printhead modules,
Only one diced printhead module is required to form a carriage-type printhead (U.S. Pat.
It is possible to stack multiple printhead modules to improve resolution or provide multicolor with a carriage-type printhead, as disclosed in US Pat. No. 33,491).

As shown in FIG. 2, a printhead module 17 (shown with its subparts) is adhered to a manifold 18 and a heatsink 16 to complete the manufacture of a thermal ink jet printhead. An adhesive 14 such as silver epoxy is applied to the heat sink 16 and the print head module 17 is bonded to the heat sink 16 by curing the adhesive 14 (S
11 to S13). The printed wiring board (PWB) is used for a heat sink (S14), and is wire-bonded to an addressing electrode of a heater plate (S1).
5). Lastly, the manifold 18 is formed by, for example, using the RTV sealing material 19 so that the print head module 1 can be used.
7 and then the manifold 18 is again secured to the heat sink 16 using epoxy (S16-S1).
8).

[0010]

The above-mentioned manufacturing method is disadvantageous for the following reasons. (1) It is difficult to accurately position and dice the wafer assembly. (2) The use of the adhesive 13 to adhere the channel plate 15 to the heater plate 12 increases the likelihood that the channel will be blocked by the adhesive during manufacture. (3)
The large number of manufacturing steps and the delicate adhesive application process involved make the entire process time consuming and costly.

[0011]

SUMMARY OF THE INVENTION Ink manifolds and channel plates are manufactured using a two-step injection molding process. Preferably, the ink manifold is made of a hard plastic material and the channel plate is made of an elastomeric material so that no seal is required between the channel plate, the manifold and the heater plate. That is, the elastomeric channel plate is self-sealing to the manifold and heater plate.

[0012] The combined manifold and channel plate provide a drop-on-demand thermal and piezo inkjet printhead, as well as liquid from a continuous stream of drops for marking the print media with non-deflecting drops. It can be used in a variety of inkjet printheads, including inkjet printheads that utilize electrostatic attraction to selectively deflect drops into a gutter. Printheads made from combined manifolds and channel plates can be used for carriage-type printheads or full-width staggered array printheads.

When manufacturing a thermal ink jet printhead according to the present invention, a plurality of heater plates are manufactured by conventional methods, for example in a silicon wafer. Individual heater plates are separated (eg, by dicing or the like) from the silicon wafer without first bonding the silicon wafer to another silicon wafer having a plurality of channel plates. Each individual heater plate is attached to the heat sink in a conventional manner. An integrated manifold / channel plate (also referred to as a manifold) is aligned with the heater plate such that each heater element on the heater plate cooperates with a corresponding channel in the channel plate. . The fixing element on the manifold is mounted on the heat sink so that the channel plate and the heater plate are in contact and are sealed from each other.

[0014] The total number of processes required is substantially less than the number of processes required in conventional ink jet manufacturing processes.

The present invention is applicable to any type of ink jet printhead having a channel plate attached to an ink manifold. That is, in the present invention, an actuating means for ejecting ink droplets from channels other than the heat-resistant element can also be used.

The present invention is a two-step injection molding method for manufacturing a combined manifold and channel plate for use in an ink jet print head, comprising: a) connecting a suction port, a discharge port, a suction port and a discharge port. Injection molding a manifold having a passage; and b) injection molding a channel plate in the manifold having a plurality of channels and a reservoir communicating the plurality of channels and the manifold outlet. And wherein said manifold and said channel plate are injection molded from materials having different physical properties.

[0017]

[0018]

3 to 5 show an injection molded ink manifold 22 having an injection molded channel plate 21 therein for forming a manifold 20 according to an illustrated embodiment of the present invention. The manifold 22 has an ink suction port 24 for receiving ink from an external ink supply device (not shown) and an ink discharge port 26 for supplying ink to the channel plate 21.
The ink suction port 24 is in fluid communication with the ink discharge port 26 via an ink passage 28 in the ink manifold 22. In addition, the manifold 22 has two posts 22a, 22b that act as means for mounting the manifold 20 on a heat sink. Also, manifold 2
2 has a support column 22c, the function of which will be described later. Manifold 22 is manufactured by Union Carbide, Inc.
n Carbide) Polysulfone (registered mark), Gneral Electri
Preferably, it is made of c) Ultem (registered mark) or a hard plastic material such as a suitable liquid crystal polymer.

The channel plate 21 has an ink discharge port 26.
Is injection molded into a manifold 22 adjacent to. The channel plate 21 can have the conventional structure of a channel plate, and further has an open recess forming a reservoir 23 on one surface that receives ink from ink outlets 26 of the manifold 22. The reservoir 23 is connected to a plurality of channels 25 that direct ink to nozzles 27 formed at the ends of the channels 25. Channel 2
1 is an olefinic thermoplastic elastomer such as Kraton (registered mark) of Shell Chemical Company.
It is preferably made of an elastomeric material such as tomer).

The dual injection molding process involves the
0 to produce The dual injection molding process is well known and will be briefly described below. The injection molding process pressure injects the hot melt polymer resin (via a lead screw ram, hydraulic ram or electric ram) into a mold (split die) or mold that is clamped together. The split die is a cavity or group of cavities machined from hardened tool steel to form negative impressions of the part being molded (i.e., manifold 22 and channel plate 21). Have. As is well known, programmable controllers automatically control various mechanical fitting characteristics, such as heating and cooling lines, process control sensors, injectors, alignment pins and gate devices used during the injection molding process.

To manufacture the manifold 20, two different molding cycles for the manifold 22 and the channel plate 21 are made, each consisting of two melts of different composition. In the first molding cycle, the mold of the channel plate 21 is inserted into the negative mold hole of the mold. As explained earlier, typically a hydraulic cylinder clamps the split die to form a mold. Further, a high heat melting plastic such as polysulfone (registered mark) is pressure injection molded into the mold.

[0022] To control the flow of the hot melt plastic in the mold, the mold can be rotated and / or advanced between two different injection systems in a conventional manner. In addition, the internal gate and the external valve of the mold are opened or closed to direct the hot melt plastic into the negative mold cavity of the manifold 22. Also, the overheating and cooling of the molten plastic is facilitated by the internal gate and the external valve, and the maintenance of an appropriate clamping pressure by the hydraulic cylinder is also facilitated. The mold of the channel plate 21 located in the mold prevents the molten plastic for the manifold from flowing into the area forming the channel plate 21. The hot mold and hot melt plastic are cooled to form a hard plastic manifold 22. Thereafter, the mold of the channel plate 21 is removed.

In the second molding cycle, Kraton (Kr
It is preferable that a dissolving elastomer such as aton (registered mark) is pressure-injected into the negative mold hole of the channel plate 21.
Since the injection molded manifold 22 occupies the space in the manifold mold cavity, the dissolving elastomer is
1 within the mold cavity. The mold cavity in the channel plate 21 has one or more protrusions 2 extending into the recesses in the manifold 22.
1a (see FIG. 6), whereby the channel plate 21 and the manifold 22 are entangled. The mold hole of the elastomer channel plate 21 is the plastic manifold 2
The elastomer channel plate 21 is securely attached to the manifold 22 when the melted elastomer is cooled and split open in the mold to mate with the second mold cavity.
Accordingly, the elastomeric channel plate 21 is injection molded into the injection molded manifold 22. By double injection molding, a print head suitable for a carriage type printer or a full width staggered array type printer can be manufactured.

The particular shape of the mold used to manufacture the manifold will vary depending on the shape of the manifold and channel plate being formed, and this particular shape will depend primarily on the type of printer in which the printhead will be used.

FIGS. 6, 7 and 8 show a thermal inkjet printhead and a process for manufacturing a thermal inkjet printhead according to one embodiment of the present invention. An ink manifold 22 having an elastomer channel plate 21 is injection molded (S101), a silicon wafer including a plurality of heater plates 12 is manufactured, diced, washed, and the heater plate is separated from the diced wafer (S102). ~ S105)
Later, the heater plate 12 is bonded to the heat sink 16 with an adhesive using, for example, silver epoxy 14 (S106 to S108). Printed wiring board (PWB)
Is attached to the heat sink and the heater plate 12
Wire bonding (S109 to S110).
Posts (posts) 22 arranged at each end of the manifold 22
a, 22b are connected to the opening 1 formed in the heat sink 16.
6a, 16b and then melting the ends of the posts 22a, 22b to attach the manifold 20 to the heat sink 16, thereby completing the manufacturing process (S111-S113). The heater plate 12 is clamped between the heat sink 16 and the channel plate 21. When the channel plate 21 is made of an elastomer, the channel plate 21 and the heater plate 12
A liquid tight seal is provided between them, which eliminates the need for an adhesive.

FIGS. 9 and 10 show the completed thermal ink jet print head 30. FIG. As shown in FIG. 10, the heater plate 12 is connected to a printed wiring board (PWB) 32 for controlling a heating element on the heater plate 12 using a wiring 34. The PWB 32 is disposed in a space formed between the manifold 22 and the heat sink 16. The post 22c helps maintain this space and acts as a stabilizing support for the manifold.

As shown in FIG. 9, the nozzle 27 is substantially rectangular. The nozzle may have a triangular shape or another shape. In addition, channels having non-uniform profiles (contours) can be formed (e.g., the ink channel suction port can have a different cross section than the ink channel discharge port).

The number of steps required to form a thermal ink jet printhead is greatly reduced when compared to conventional manufacturing methods. By reducing the number of steps, assembly time and manufacturing cost are also reduced. Further, since the epoxy 13 and the RTV seal 19 are eliminated from the manufacturing process, there is less likelihood that the channels of the channel plate will be clogged by the epoxy and RTV seals, respectively, during the bonding of the heater plate and the manifold. The yield of this process for inkjet printheads is increased.

The number of steps for manufacturing a thermal ink jet printhead is reduced using the above-described manifold having an elastomeric channel plate and a method of manufacturing the same. Furthermore, expensive semiconductor wafers need not be used to manufacture the channel plates of the thermal inkjet printhead. Furthermore, the channel and the heater plate are attached to each other without using an adhesive. Further, it will be appreciated that the elastomeric channel plate may be formed such that the bottom surface of the channel plate is completely flush with the bottom surface of the manifold.

FIGS. 11 and 12 are cross-sectional views of a channel plate according to a further modification of the present invention after being attached to a heater plate. The channel plate 21 in FIGS. 11 and 12 can be formed integrally with the manifold or can be formed remotely from the manifold by a one-step injection molding process. The channel plate 21 in FIGS. 11 and 12 is preferably made of an elastomeric material when manufactured with a manifold, but a non-elastomer material such as a ceramic green tape (Green Tape) when not integrally formed with the manifold. It is also possible to manufacture with.

The channel plate 21 in FIGS. 11 and 12 differs from the above-mentioned channel plate in that pits 29 are formed in each channel 25 of the channel plate 21. The pits 29 are arranged in a portion of the channel 25 on the heater plate 12 corresponding to the heater element 12a. By providing the pits 29, it is not necessary to provide pits in the polyimide protective layer 12b. The polyimide protective layer 12b is provided on the upper surface of the heater plate 12, and protects the circuit 12c on the heater plate 12 from the corrosion effect of the ink in the channel 25. This makes it possible to form the polyimide protective layer 12b as a very thin layer. For an example of a conventional pit formed in a polyimide protective layer, see Hawkis.
See FIG. 2 of U.S. Pat. No. 4,774,530 to U.S. Pat.

[0032]

In addition to saving polyimide, time is saved by forming pits 29 in the channel plate 21 and heater wafer yield (current processes for forming polyimide layers are imposed on the process). Cost, depending on the stiffness) and the total number of process steps is reduced. Further, for example, a pit shape change such as a sidewall profile or a cavity shape, which cannot be realized with polyimide, can be performed.

The present invention is also applicable to an ink jet printer that uses means other than heat to discharge droplets through a nozzle.

[Brief description of the drawings]

FIG. 1 is a block diagram of a conventional process for manufacturing a thermal inkjet printhead.

FIG. 2 is an exploded front view of a conventional thermal ink jet print head provided on a heat sink.

FIG. 3 is a front view of a channel according to an embodiment of the present invention.

FIG. 4 is a side view of the channel of FIG. 3;

FIG. 5 is a cross-sectional view of the manifold along line 5-5 in FIG. 3;

FIG. 6 is a front view of a print head manufactured by a manifold according to an embodiment of the present invention, and is an exploded view of the print head.

FIG. 7 is a front view of a print head manufactured by a channel according to an embodiment of the present invention.

FIG. 8 is a block diagram of a manufacturing process of a thermal inkjet print head according to an embodiment of the present invention.

FIG. 9 is a front view of a thermal ink jet print head having a manifold according to an embodiment of the present invention.

FIG. 10 is a cross-sectional view of the thermal inkjet printhead of FIG. 9 taken along line 9-9 of FIG.

FIG. 11 is a cross-sectional view of a modified channel plate having pit characteristics.

FIG. 12 is a sectional view taken along lines 11-11 in FIG. 11;

[Explanation of symbols]

 12 Heater Plate 16 Heat Sink 20 Channel 21 Channel Plate 22 Ink Manifold 23 Reservoir 24 Ink Absorption Port 25 Channel 26 Ink Discharge Port 27 Nozzle 28 Ink Passage

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-57-178765 (JP, A) JP-A-2-125738 (JP, A) JP-A-2-187344 (JP, A) West German patent application published 3438033 (DE, A1) (58) Fields investigated (Int. Cl. ⁷ , DB name) B29C 45/00-45/84 B41J 2/16

Claims (1)

(57) [Claims] 1. A two-step injection molding method for manufacturing a combined manifold and channel plate for use in an inkjet print head, comprising: a) a suction port, a discharge port, and a passage connecting the suction port and the discharge port. B) injection molding a channel plate having a plurality of channels and a reservoir communicating with the plurality of channels and the manifold outlet in the manifold; A step wherein the manifold and the channel plate are injection molded from materials having different physical properties.